For applications in which large volumetric flows are controlled, pilot-controlled pressure control valves are preferably used instead of directly controlled valves. A high volumetric flow means both large opening cross sections of the valves for large strokes and large flow forces which counteract the magnetic force of the magnet system to be actuated as a disturbance variable. To resolve these problems, the magnet system would have to be dimensioned to be correspondingly large for directly controlled valves.
For applications of this type, valves are known in the prior art which have hydraulic piloting, see DE 103 25 178 A1. This known solution is characterized, compared to other proposed solutions which are prior art and which are disclosed by U.S. Pat. No. 6,286,535 B1, in that the valve is able to set a pressure value of 0 bar on the user connection when the magnet system is not actuated. For the valves disclosed in that U.S. patent, this ability is not possible because, according to its construction, the control piston is returned to its end position by a clamped compression spring when the magnet system has not been actuated. Due to this mechanical configuration, these valves still have a pressure level which corresponds to the force of the clamped spring when there is no electrical control signal of the magnet system present.